Creating a polygon plane with different sections / components
I suppose you want the extrude part to be strict squares. Here are some ways to do it (among others):

1)


Create a plane and create an edge loop in its middle with a ctrl R.
Scale your plane on the same axis, for example 3 times (S Y 3).
ctrl Rand + to create as many edge loops as necessary on the orthogonal axis.




2)


Create a plane and Subdivide it for example 5 times (use the parameters on the bottom of the left menu).
Delete a part of the plane so that you have the length you want.




3)


Create a plane, subdivide it, enable the Snap option and its options.
Duplicate the first subdivided plane as many time as you want, the Snap option allows you to stick to the previous copy and to merge the vertices.




4)


Subdivide a plane
Add an Array modifier and choose the Count you want
Apply the modifier in Object mode